US4368383A - System for focus detection utilizing a photoelectric sensor array - Google Patents
System for focus detection utilizing a photoelectric sensor array Download PDFInfo
- Publication number
- US4368383A US4368383A US06/294,724 US29472481A US4368383A US 4368383 A US4368383 A US 4368383A US 29472481 A US29472481 A US 29472481A US 4368383 A US4368383 A US 4368383A
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- US
- United States
- Prior art keywords
- photoelectric conversion
- electric signals
- generating
- signals
- amplifying
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
- G03B3/00—Focusing arrangements of general interest for cameras, projectors or printers
- G03B3/10—Power-operated focusing
Definitions
- the present invention relates to a light measuring device for measuring the intensity distribution of light, and more particularly to a light measuring device for use in a focus detecting apparatus for example for a camera.
- the focus detecting apparatus for a camera it is already known to form a light image of an object on a photoelectric sensor array and to detect the focusing of said object by the photoelectric output of said array representing the intensity distribution of said light image.
- the photoelectric output from said photoelectric sensor array consisting of time-sequential pulses corresponding to the light intensities on the photoelectric sensors, often becomes unable to provide the difference information because of the saturation of the signal amplifier in case the object has a high average luminance giving rise to a high illumination intensity of the light image.
- the information required for the focus detection is the distribution of the light intensity, i.e. the difference of the output signals from the photoelectric sensors. Consequently it is desirable, in the amplification of the time-sequential pulse output from the photoelectric sensor array, to amplify only the difference with respect to a reference voltage selected suitably according to the DC level of said output.
- the object of the present invention is to provide a light measuring device capable of amplifying the difference of the time-sequential pulse output signals from the photoelectric sensor array regardless of the magnitude of said pulse output signals.
- a light measuring device comprising optical system means; means comprising a photoelectric sensor array having a plurality of photoelectric sensors for receiving the light passing through said optical system means and generating electric signals respectively corresponding to the intensity of light received by said photoelectric sensors as time-sequential signals of a determined interval; means for generating a comparison signal of a determined magnitude related to the output level of said electric signals; and processing means adapted to receive said electric signals and said comparison signal to generate output signals related to the difference of said signals in a sequential manner.
- FIG. 1 is a circuit diagram of a first embodiment of the light measuring device of the present invention
- FIGS. 2A to 2C are charts showing the gate pulses to be employed in the circuit shown in FIG. 1;
- FIGS. 3A and 3B are charts showing the examples of the processed signal voltages
- FIG. 4 is a circuit diagram of a second embodiment of the light measuring device of the present invention.
- FIGS. 5A and 5B are charts showing the examples of the processed signal voltages.
- FIG. 1 shows a first embodiment of the light measuring device of the present invention, wherein a photodiode array 1 consisting of four photodiodes D1-D4 and a switching element array 2 consisting of field-effect transistors S1-S4 are connected to a sample hold circuit 3 provided with an operational amplifier 3a, a feedback condenser 3b and a reset switch S5, and the output of said sample hold circuit 3 is connected through a field-effect transistor S6 to a processing circuit 5 consisting of a condenser 4 and operational amplifiers 5a and 5b. Further the output of said processing circuit 5 is connected through field-effect transistors S10-S40 to hold circuits 6-9 having operational amplifiers 6a-9a.
- the field-effect transistors S1-S4 are rendered momentarily conductive upon receipt at the gates G1-G4 thereof of drive pulses delayed in succession by a time t1 within a cycle period T as shown in FIG. 2A.
- the reset switch S5 is rendered conductive by gate pulses G5 as shown in FIG. 2B immediately before the conductive states of said field-effect transistors S1-S4 to dissipate the charge previously transferred from the photodiode and to prepare for the charge transfer from the succeeding photodiode.
- the sample hold circuit 3 in response to the successive conduction of the field-effect transistors S1-S4 with a delay time t1, the sample hold circuit 3 generates the output voltages e1-e4 as shown in FIG. 3A corresponding to the intensity of the light received by the photodiodes D1-D4.
- the field-effect transistor S2 is rendered conductive so that V 3 becomes equal to e 2 .
- V 5 V r +(1+N 2 ) (e 4 -e 1 ) is memorized in the hold circuit 9.
- the hold circuit 6 memorizes the input voltage V r to the operational amplifier 5a regardless of the value e 1 while the hold circuit 7 memorizes the difference between e 2 and e 1 appropriately amplified and added with the value V r , and hold circuits 8 and 9 similarly memorize the difference between e 3 and e 4 and e 1 appropriately amplified and added with the value V r .
- FIG. 4 shows a second embodiment of the present invention, wherein the sample hold circuit 3 connected to the photodiode array 1 and the switching element array 2 generates, in a similar manner as in the first embodiment shown in FIG. 1, output voltages e1-e4 corresponding to the intensity of light received by the photodiodes D1-D4.
- the uninverted input terminal of a differential amplifier 10 composed of an operational amplifier 10a and resistors R11-R14 receives the output voltage V3 from the sample hold circuit 3 while the inverted input terminal of said differential amplifier receives the feedback voltage V12 to generate an output signal V10 related to the difference between said inputs V3 and V12.
- the output signal V10 can be represented by:
- the voltage V 10 assumes the values e 1 '-e 4 ' respectively corresponding to the photoelectric output voltages e 1 -e 4 each subtracted by a constant comparison voltage V 12 .
- the output signals V 10 are stored in the hold circuits 60-90 respectively provided with memory condensers 60b-90b through field-effect transistors S100-S400. Said transistors are rendered conductive, in a similar manner as in the foregoing first embodiment, by gate pulses G10-G40 shown in FIG.
- said memory condensers 60b-90b respectively store the voltages e 1 '-e 4 ' respectively equal to the photoelectric output voltages e 1 -e 4 each subtracted by the comparison voltage V12, said stored voltages being taken out as the output voltages V100-V400 for focus detection.
- the memorized output voltages e 1 '-e 4 ' are averaged in an averaging circuit 11 and compared with a standard voltage V m . If the resistances connected to the hold circuits are selected mutually equal and equal to four times of the feedback resistance of the operational amplifier 11a, the output voltage V11 of said averaging circuit is represented by:
- the above-mentioned output V 12 is supplied as the comparison feedback voltage to the inverted input terminal of the aforementioned differential amplifier 10. In this manner the output V 12 is the time-integrated difference between a constant reference voltage V r and the averaged value e' of the memorized difference signals.
- the average value e' of the voltages e 1 '-e 4 ' stored in the memory condensers 60b-90b is selected equal to the determined reference voltage V r -V n -2V m .
- the output signals V100-V400 containing the information of the intensity distribution but having a constant average level regardless of the DC level of the photoelectric output signals, thus avoiding the saturation of the amplifier.
- FIGS. 5A and 5B show the photoelectric output signals e 1 -e 4 from the photoelectric sensor array while FIG. 5B shows the difference output signals e 1 '-e 4 ' obtained by subtraction of the reference voltage V12 from said signals e 1 -e 4 and amplification by a determined gain in the differential amplifier 10 and stored in the condensers 60b-90b.
- the feedback system is controlled in such a manner that the average value e' of said difference signals e 1 '-e 4 ' becomes equal to the determined reference voltage V r , the difference signals e 1 '-e 4 ' become distributed around the reference voltage V r as shown in FIG.
Abstract
Description
V.sub.5 =N.sub.1 ·N.sub.2 ·V.sub.r -(1+N.sub.1)·N.sub.2 ·V.sub.4 +(1+N.sub.2)V.sub.3 (1)
N.sub.1 ·N.sub.2 =R.sub.2 ·R.sub.4 /R.sub.1 ·R.sub.3 =1
V.sub.5 =V.sub.r +(1+N.sub.2)(V.sub.3 -V.sub.4) (2)
V.sub.10 =-R.sub.12 ·(V.sub.3 -V.sub.12)/R.sub.11
V.sub.11 =2V.sub.m -e'
V.sub.12 =a+b∫(V.sub.n -2V.sub.m +e')dt
V.sub.n -2V.sub.m +e'=0
Claims (13)
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP14722778A JPS5574426A (en) | 1978-11-30 | 1978-11-30 | Photometer circuit |
JP53-147227 | 1978-11-30 | ||
JP53-158693 | 1978-12-25 | ||
JP15869378A JPS5587014A (en) | 1978-12-25 | 1978-12-25 | Amplifier of light measurement circuit |
Related Parent Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US06097868 Continuation | 1979-11-27 |
Publications (1)
Publication Number | Publication Date |
---|---|
US4368383A true US4368383A (en) | 1983-01-11 |
Family
ID=26477836
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US06/294,724 Expired - Lifetime US4368383A (en) | 1978-11-30 | 1981-08-20 | System for focus detection utilizing a photoelectric sensor array |
Country Status (2)
Country | Link |
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US (1) | US4368383A (en) |
DE (1) | DE2947951A1 (en) |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4447719A (en) * | 1981-02-03 | 1984-05-08 | Nippon Kogaku K. K. | Automatic focus adjusting apparatus using weighted average means |
US4522492A (en) * | 1981-07-10 | 1985-06-11 | Canon Kabushiki Kaisha | Distance measuring device |
US4542289A (en) * | 1982-04-08 | 1985-09-17 | Fuji Electric Company Ltd. | Automatic focusing apparatus including image contrast detection means |
US4573784A (en) * | 1982-12-11 | 1986-03-04 | Canon Kabushiki Kaisha | Focus detecting apparatus |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4047187A (en) * | 1974-04-01 | 1977-09-06 | Canon Kabushiki Kaisha | System for exposure measurement and/or focus detection by means of image senser |
US4173402A (en) * | 1977-03-10 | 1979-11-06 | Ricoh Company, Ltd. | Optoelectronic sensing apparatus |
US4184968A (en) * | 1978-02-13 | 1980-01-22 | Honeywell Inc. | Auto focus system |
-
1979
- 1979-11-28 DE DE19792947951 patent/DE2947951A1/en not_active Withdrawn
-
1981
- 1981-08-20 US US06/294,724 patent/US4368383A/en not_active Expired - Lifetime
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4047187A (en) * | 1974-04-01 | 1977-09-06 | Canon Kabushiki Kaisha | System for exposure measurement and/or focus detection by means of image senser |
US4173402A (en) * | 1977-03-10 | 1979-11-06 | Ricoh Company, Ltd. | Optoelectronic sensing apparatus |
US4184968A (en) * | 1978-02-13 | 1980-01-22 | Honeywell Inc. | Auto focus system |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4447719A (en) * | 1981-02-03 | 1984-05-08 | Nippon Kogaku K. K. | Automatic focus adjusting apparatus using weighted average means |
US4522492A (en) * | 1981-07-10 | 1985-06-11 | Canon Kabushiki Kaisha | Distance measuring device |
US4542289A (en) * | 1982-04-08 | 1985-09-17 | Fuji Electric Company Ltd. | Automatic focusing apparatus including image contrast detection means |
US4573784A (en) * | 1982-12-11 | 1986-03-04 | Canon Kabushiki Kaisha | Focus detecting apparatus |
Also Published As
Publication number | Publication date |
---|---|
DE2947951A1 (en) | 1980-06-12 |
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